1. Field of the Invention
This invention relates in general to the construction of bearings and in particular to a new and useful method of forming a bearing of a cobalt alloy with a boride coating thereon.
The present invention is particularly applicable to component parts which are in frictional contact and which may be referred to as bearing parts. Such parts include journal pins of pointer shafts for electrical measurement instruments and bushings and journals of any kind and particularly those used in the field of precision mechanics. Bearing parts of particularly high hardness especially bearing journals in conical and cylindrical bearings are made at the present time of sintered hard metals and consequently these hard metals are affected by the high brittleness typical of such materials and in some instances they even break during the mounting thereof. Metallic bearing parts of lower hardness than the hard metal bearings frequently employed are subject to considerable wear which is not infrequently connected with corrosion phenomena.
2. Summary of the Invention
In accordance with the invention a bearing part is provided which is made of an age hardening cobalt alloy coated at least over its surface portions which are exposed to bearing friction with a boride layer. Such bearing parts have excellent frictional, wearing and endurance properties and are free from the drawbacks which occur with the prior art devices as mentioned above. In spite of the very high superficial hardness, such bearing parts are not brittle and show a high resistance to corrosion and are non-magnetic.
In accordance with the method of the invention a bearing part is manufactured of a ductile cobalt alloy which is capable of being age hardened by heat treatment which is shaped in the desired form of the bearing and thereafter is coated with a boride layer over the area which is to be employed as a bearing surface. The coating is accomplished either from the vapor phase or by diffusion from a solid phase and is carried out during a heat treatment at a temperature in the range of from 550.degree. C. to 900.degree. C. and by the same heat treatment an age hardening process is effected.
Accordingly it is an object of the invention to provide an improved bearing construction comprising a cobalt alloy base and a covering on a bearing surface of a boride.
A further object of the invention is to provide a method of forming a bearing which comprises forming a ductile alloy of cobalt and age hardening it by heat treatment and depositing during the same heat treatment a layer of boride over the alloy at a temperature of from between 550.degree. C. to 900.degree. C.
A further object of the invention is to provide a bearing structure which is simple in design, rugged in construction and economical to manufacture.
For an understanding of the principles of the invention, reference is made to the following description of a typical embodiment thereof as illustrated in the accompanying drawing.